The interior of the nostril, known as the nasal cavity, is a complex chamber designed to prepare inhaled air for the lungs. It serves multiple functions, including warming, humidifying, and filtering the air before it travels into the respiratory system. The nasal cavity is a structured environment made up of specialized tissues, dividing walls, and bony shelves.
The Initial View: The Nasal Vestibule
The entrance to the nostril is the nasal vestibule, the immediate area behind the external opening. This region is lined by specialized skin that is continuous with the skin outside the nose. It is covered by stratified squamous epithelium, a robust tissue that protects the delicate internal structures from the outside environment.
Within the vestibule, coarse hairs called vibrissae act as the first line of defense against airborne particles. These hairs trap larger pieces of dust and debris, preventing them from traveling deeper into the nasal passages. The vibrissae are coated in mucus, which helps these natural filters capture the inhaled contaminants. This section transitions deeper into the nose at the limen nasi, where the skin-like lining changes to the respiratory membrane of the main nasal cavity.
The Central Divider: The Nasal Septum
Directly separating the left and right nasal passages is the nasal septum, a wall that runs vertically from the front to the back of the nose. The septum ensures the air is divided into two distinct, parallel streams. This central divider is composed of cartilage in the front and bone toward the back.
The anterior portion is formed by the septal nasal cartilage, a flexible, quadrilateral plate of hyaline cartilage. This cartilaginous section provides both shape and resilience to the lower part of the nose. Deeper inside, the septum gains structural rigidity from bones such as the perpendicular plate of the ethmoid bone and the vomer. The entire surface of the septum appears smooth, creating a medial wall for each side of the nasal cavity.
The Inner Walls: Turbinates and Air Passages
Looking beyond the vestibule reveals the lateral walls of the nasal cavity, which are highly convoluted due to shelf-like structures called conchae, or turbinates. There are usually three pairs of these structures—the inferior, middle, and superior turbinates—that project inward like curved ridges. The turbinates are complex structures made of thin bone covered by a thick layer of soft tissue.
This design makes the inner nostril appear irregular, almost like a maze. The purpose of this architecture is to dramatically increase the internal surface area for air modification. The spaces created beneath each turbinate are known as meatuses, which serve as the main air passages and direct the flow of air. The largest of these is the inferior turbinate, which significantly contributes to the way air is warmed and humidified.
The Specialized Surface: Mucosa and Blood Vessels
The entire inner surface of the nasal cavity, including the septum and turbinates, is covered by a specialized lining known as the nasal mucosa or mucous membrane. This tissue secretes mucus, which traps fine particles that escaped the vibrissae and keeps the air moist. The surface has a moist, glistening appearance and displays a characteristic pink or reddish color.
This vibrant color is a result of a dense network of delicate blood vessels lying just beneath the surface. This rich vascular supply is necessary, as the vessels help warm the incoming air to body temperature. The high concentration of small, fragile blood vessels, particularly in the anterior part of the septum (known as Kiesselbach’s plexus), is why the nose is prone to bleeding when the lining is irritated or damaged. The submucosal layer of the turbinates also contains large venous spaces that can swell, regulating airflow resistance within the cavity.